#include <stdio.h>
int main(int argc, char const *argv[]) {
    float toobig = 3.4E38 * 100.0f;//浮点数上溢
    float a = 2.0e20 + 1.0 - 2.0e20;//浮点数下溢
    printf("%e\n",a);
    printf("%e\n",toobig);
    return 0;
}
